Tube pump

ABSTRACT

The tube pump includes a base that holds a drive shaft; a rotor portion that rotates with the driving shaft, the rotor portion having a pair of rollers; a casing having a U-shaped internal surface along which an elastic tube is arranged, the casing being mounted on the base so that the casing can slide with respect to the base in a direction parallel to the linear portions; a cover that is rotatably mounted on the casing; a moving mechanism including a rack that is formed on the base and a pinion that is fixed to the rotation shaft of the cover. The moving mechanism moves the casing to the operating position where the roller deforms the elastic tube when the cover closes, and the moving mechanism moves the casing to the exchange position where the roller comes apart from the elastic tube when the cover opens.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tube pump that deforms an elastictube by rotating rollers to send out liquid in the elastic tube.Especially the present invention relates to a tube pump mounted onartificial dialysis equipment etc. that enables easy attachment andremoval of the elastic tube.

2. Prior Art

This kind of tube pump is disclosed in Japanese unexamined patentpublication No. Hei 6-218042, for example. The tube pump disclosed inthe publication is provided with a casing body having a semicircularinternal surface, a drive shaft located at the center of the semi-circleand a rotor portion that rotates with the drive shaft. The rotor portionhas a pair of rollers whose rotation axes are decentered from the driveshaft. For operation, arrange an elastic tube along the internal surfaceof the casing body and rotate the rotor portion to deform the elastictube with compression between the internal surface and the rollers tosend liquid in the elastic tube.

Since the tube pump sends liquid by deforming the elastic tube, the tubetends to deteriorate, which requires frequent exchange of the tube.Further, when this kind of tube pump is used in artificial dialysisequipment, the drawing direction of the elastic tube may be changed tomatch layout of the artificial dialysis equipment with respect to a bedof a patient or to avoid frequently inserting shunt needles into thesame arm of a patient. However, since the elastic tube is pinchedbetween one roller and the internal surface of the tube pump, it takesmuch expense in time and effort to exchange the tube even if the rotorportion stops.

Therefore, the tube pump of the above publication divides the casingbody into a movable casing that forms a part of the semicircularinternal surface and a fixed casing that forms the other portion. Thisenables to exchange the tube under the condition where the roller comesapart from the elastic tube by separating the movable casing from thefixed casing. With this construction, the elastic tube can be easilyattached and removed.

However, since the tube pump disclosed in the above publication dividesthe semicircular internal surface to which large pressure is applied bythe rotation of the rotor portion in operation into two portions, it isdifficult to keep structural strength. Therefore, the movable and fixedcasings are formed from metal, which increases the cost of the tube pumpin comparison with that with plastic casings. Although the publicationdescribes that the casings may be made from plastic, if the casingshaving the same structure are made from plastic, there is a highprobability that the casings break due to lack of strength in reality.

Further, the tube pump of the above publication slides the movablecasing in response to the opening and closing operations of the casingcover. However, since the casing to which large pressure is applied isdivided as described above, a solenoid to lock the movable casing at theposition connecting to the fixed casing and a sensor that detects theopening and closing of the cover to control the solenoid are required,which complicates the construction of the tube pump.

Still further, the tube pump of the publication has a pair of tube clamparms that hold the tube at the entrance and exit positions of the pump.However, since the clamp arms must be operated manually, the operationof the clamp arms for exchanging the tube is complicated.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a tube pump thatcan increase structural strength of a casing so that it can be made fromplastic with easy attachment and removal of an elastic tube.

A second object of the present invention is to provide a tube pump thatdoes not require a mechanism for locking a casing at an operatingposition on the precondition that a roller changes its position inresponse to opening/closing of a cover between the operating positionwhere the roller deforms the elastic tube and an exchange position wherethe roller comes apart from the elastic tube.

A third object of the present invention is to provide a tube pump thatcan automatically operate clamp arms arranged at entrance and exitpositions of the pump.

In order to achieve the first and second objects, a tube pump of a firstaspect of the present invention includes:

-   -   a base that holds a drive shaft that connects with and is driven        by a motor;    -   a rotor portion that rotates with the driving shaft, the rotor        portion having a pair of rollers each of which has a rotating        shaft decentered from the drive shaft;    -   a casing having a U-shaped internal surface that includes a        semicircular portion and parallel linear portions connected to        both ends of the semicircular portion along which an elastic        tube is arranged, the casing being mounted on the base so that        the casing can slide with respect to the base in a direction        parallel to the linear portions;    -   a cover that is rotatably mounted on the casing at the outside        of the semicircular portion, the cover covering the portion        surrounded by the internal surface at its closing position;    -   a moving mechanism including a rack that is formed on the base        and a pinion that is fixed to the rotation shaft of the cover        and engages with the rack, the moving mechanism moving the        casing with respect to the base to an operating position where        the roller deforms the elastic tube arranged along the internal        surface when the cover closes, and the moving mechanism moving        the casing with respect to the base to an exchange position        where the roller comes apart from the elastic tube when the        cover opens.

With this construction, since the casing to which large pressure isapplied is not separated, the structural strength becomes larger, whichkeeps the casing intact even if it is made from plastic. Further, whenan elastic tube is located along the internal surface of the casing andthe cover is closed, the rotation of the rotor portion deforms theelastic tube between the roller and the internal surface to send outliquid in the elastic tube. When the cover is opened, the elastic tubecan be easily exchanged.

A step portion (a level difference portion) may be formed on theinternal surface of the casing so that the diameter of the semicircularportion at the side of the cover becomes larger than the other side.Further, a convex rim, which can insert inside the internal surface, isformed on the cover at the position opposite to the step portion. Thestep portion and the convex rim function as a means for guiding theelastic tube that is arranged along the internal surface.

In order to achieve the above-described third object, a tube pump of asecond aspect of the present invention has the following characteristicfeatures. That is, the base is provided with a pair of clamp arms thathold entrance and exit portions of the elastic tube to the pump,respectively, the base end of each clamp arm is rotatably attached to apivot that is vertical to the axis of the drive shaft and is parallel tothe linear portions, each clamp arm has a tip end that is formed to holdthe elastic tube and has a small roller at a middle portion thereof. Thebase has a biasing mechanism that applies bias pressure to the clamparms so that the small rollers move closer and the clamp arms releasethe elastic tube. A connecting projection, which intrudes between thesmall rollers when the cover closes, is formed on the cover.

With this construction, when the cover opens, since the tip ends of theclamp arms release the elastic tube due to the bias pressure applied bythe biasing mechanism, the elastic tube can be easily exchanged. Whenthe cover closes, the connecting projection of the cover intrudesbetween the small rollers and separates them from each other, whichrotates the clamp arms against the bias pressure applied by the biasingmechanism. Therefore, the tip ends of the clamp arms are pressed to theelastic tube and the clamp arms hold the elastic tube.

As described above, since the elastic tube is automatically held andreleased in response to the opening and closing of the cover withoutmanual operation of the clamp arms, the elastic tube can be easilyexchanged.

In addition, a permanent magnet may be mounted on the rotor portion atthe position opposite to the casing and a magnetic sensor may beinstalled on either of the casing and the base to determine the rotationposition of the rotor portion by detecting the magnetic flux of thepermanent magnet. The output of the magnetic sensor is used to control amotor that drives the rotor portion. For instance, when the rotation ofthe rotor portion is stopped, the motor is controlled to stop one rollerat the midpoint of the semicircular portion of the casing so that themovement of the casing by the moving mechanism can come apart the rollerfrom the elastic tube. For easy exchange of the elastic tube, the rollermust come apart from the elastic tube at the exchange position. If therotor portion stops at the position where the roller faces the linearportion of the internal surface, since the roller does not come apartfrom the elastic tube when the cover opens, it becomes difficult toexchange the elastic tube. Therefore, it is preferable to predeterminethe stop position and to control the motor for driving the tube pumpaccording to the predetermined stop position.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a perspective plan view of a tube pump of an embodimentaccording to the present invention when an elastic tube is attached tothe tube pump and a cover closes;

FIG. 2 is a sectional side view of FIG. 1 along the II-II line;

FIG. 3 is a sectional front view of FIG. 1 along the III-III line;

FIG. 4 is a plan view of the tube pump of the embodiment when the coveropens before the elastic tube is removed;

FIG. 5 is a plan view of the tube pump of the embodiment when the coveropens after the elastic tube and the rotor portion are removed;

FIG. 6 is a sectional side view of FIG. 4 along the VI-VI line;

FIG. 7 is a sectional view of FIG. 1 along the VII-VII line when a tubeclamp mechanism holds the elastic tube;

FIG. 8 is a sectional view of FIG. 4 along the VIII-VIII line when thetube clamp mechanism releases the elastic tube; and

FIG. 9 is a system chart showing the entire construction of artificialdialysis equipment that employs the tube pump of the embodiment as ablood pump.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a tube pump of an embodiment according to the presentinvention will be described with reference to the drawings. Initially,an example of the use of the tube pump of the embodiment will bedescribed according to FIG. 9.

FIG. 9 shows the entire construction of artificial dialysis equipment 2that employs the tube pump 1 of the embodiment as a blood pump. Theartificial dialysis equipment 2 is provided with the tube pump 1, adialyzer 3, first and second chambers 4 and 5. The equipment 2 isincorporated in an extracorporeal circulation path of a patient P. Inaddition, the reference F in FIG. 9 indicates a cover sheet put on thebody of the patient P.

Blood collected from the arm of the patient P is drawn by the tube pump1 through the tube and is pressurized to send to the first chamber 4.The blood that is temporally accumulated in the first chamber 4 is sentto the dialyzer 3. The dialyzer 3 dialyzes and filters the blood withusing a dialyzate solution supplying line 6 to remove deleteriousmaterial and excess water. The blood after dialysis is temporallyaccumulated in the second chamber 5 and then is sent back to the arm ofthe patient P.

The construction of the above-described tube pump 1 will be describedwith reference to FIG. 1 through FIG. 8. FIG. 1 through FIG. 3 show thetube pump 1 of the embodiment when the elastic tube C is placed and thecover closes, FIG. 1 is a perspective plan view (the cover isillustrated by the two-dot chain line), FIG. 2 is a sectional side viewof FIG. 1 along the II-II line and FIG. 3 is a sectional front view ofFIG. 1 along the III-III line (a position of a rotor portion isdifferent from that in FIG. 1). FIG. 4 through FIG. 6 show the tube pump1 of the embodiment when the cover opens, FIG. 4 is a plan view beforethe elastic tube is removed, FIG. 5 is a plan view after the elastictube and a rotor portion shown in FIG. 4 are removed and FIG. 6 is asectional side view of FIG. 4 along the VI-VI line. FIG. 7 and FIG. 8show a tube clamp mechanism that holds the elastic tube C at theentrance and exit positions of the tube pump 1, FIG. 7 is a sectionalview of FIG. 1 along the VII-VII line and FIG. 8 is a sectional view ofFIG. 4 along the VIII-VIII line.

The tube pump 1 of the embodiment is provided with, as shown in FIG. 1and FIG. 2, a base 20 having a drive shaft 21 that is connected to amotor 10 through a reduction gear 11, a rotor portion 30 attached to thedrive shaft 21, a casing 40 that can slide in an arrowed X-direction inFIG. 1 with respect to the base 20 and a cover 50 that covers over thecasing 40. When the drive shaft 21 is rotated by the motor 10, the rotorportion 30 rotates together with the drive shaft 21.

The base 20 includes a fixing portion 22 for fixing the elastic tube Cat the entrance and exit positions and a holding portion 23 for holdingthe casing 40 so that the casing 40 can slide in the X-direction. At thecenter of the holding portion 23, a base opening 24 is formed forallowing the drive shaft 21 to pass through. A bearing 21 a forsupporting the drive shaft 21 is installed in the base opening 24.

The rotor portion 30 is a single unit that is detachable/attachable tothe drive shaft 21, and it consists of a rotor body 31 having a shape ofa rectangular parallelepiped to which the drive shaft 21 is inserted, apair of roller holders 32 a, 32 b attached to both sides of the rotorbody 31, and a pair of rollers 34 a, 34 b that are supported by theroller holders 32 a, 32 b via rotating shafts 33 a, 33 b decentered fromthe drive shaft 21. The roller holders 32 a and 32 b are connected tothe rotor body 31 by axial pins 35 a and 35 b mounted on diagonalpositions of the rotor body 31 so that the roller holders 32 a and 32 bcan pivot about the axial pins 35 a and 35 b, respectively. Further, thefree ends of the respective roller holders 32 a and 32 b are pushed bycompression springs (not shown) in the direction that distances the freeends from the rotor body 31.

There is a space at the center of the casing 40 for arranging the rotorportion 30 and the elastic tube C, and a sidewall surrounds the spacefrom three directions. A U-shaped internal surface 41 of the sidewallconsists of a semicircular portion 41 a and a pair of linear portions 41b, 41 c that are connected to both ends of the semicircular portion 41a. The elastic tube C is located along the internal surface 41.

Further, the casing 40 is mounted on the base 20 so that the casing 40can slide in the X-direction in FIG. 1, which is the direction of thelinear portions 41 b, 41 c, with respect to the base 20. That is, asshown in FIG. 2, FIG. 3 and FIG. 5, a projecting edge 24 a is formedalong the upper edge of a base opening 24 formed on the base 20 and acasing opening 42 is formed on the bottom of the casing 40 to connectwith the base opening 24. The casing opening 42 is larger than the baseopening 24 in the X-direction as shown in FIG. 2 and contacts theoutside of the projecting edge 24 a of the base opening 24 in aY-direction as shown in FIG. 3. A flange 42 a is formed on the edge ofthe casing opening 42 and the flange 42 a, which is stepped down fromthe casing opening 42, is sandwiched between the base 20 and a fixingplate 43 that is fitted in the base opening 42. With this construction,the casing 40 can slide in the X-direction with respect to the base 20without changing its position in the Y-direction and is held by thefixing plate 43 not to be removed.

In addition, the base 20, the casing 40 and the rotor body 31 of therotor portion 30 are made from rigid plastic. The rotor holders 32 a and32 b are made from metal or rigid plastic.

As shown in FIG. 1 and FIG. 2, the cover 50, which is made fromtransparent plastic, is provided with a dome portion 51 that covers theinside of the internal surface 41 of the casing body 40 and is fixed byscrews to the rotation axis 44 that is rotatably mounted on the one endof the casing 40. On the other end of the cover 50, a knob 52 is formedto be handled by an operator for closing and opening operations. Theknob 52 has a connecting projection 54 that is formed at the inside ofthe knob 52 towards the casing 40 to connect with the fixing portion 22of the base 20. The function of the connection projection 54 will bedescribed below.

Next, the moving mechanism that moves the casing 40 with respect to thebase 20 will be described. As shown in FIGS. 2 and 6, a rack 25 isformed on one side of the base 20 and a pinion 45 that engages the rack25 is fixed to a rotation shaft 44 that rotates with the opening/closingof the cover 50. As shown in FIGS. 1 and 4, the pinions 45 are fixed toboth sides of the rotation shaft 44 and the racks 25 are formed at thecorresponding positions.

The opening/closing operations of the cover 50 rotates the pinions 45,which changes the relative position between the pinions 45 and the racks25 in the X-direction, sliding the casing 40 with respect to the base20. When the cover 50 closes as shown in FIG. 1, the casing 40 moves theroller 34 b with respect to the base 20 to an operating position wherethe roller 34 b deforms the elastic tube C arranged along the internalsurface 41. When the cover 50 opens as shown in FIG. 4, the casing 40moves roller 34 b with respect to the base 20 to an exchange positionwhere the roller 34 b comes apart from the elastic tube C to release thedeformation.

As shown in FIG. 3, a step portion (a level difference portion) 46 isformed on the semicircular portion 41 a of the internal surface 41 ofthe casing 40 so that the diameter at the side of the cover 50 (theupper side in FIG. 3) becomes larger than the other side (the lowerside). Further, a convex rim 55, which can insert inside the largerdiameter portion of the internal surface 41, is formed on the cover 50at the position opposite to the step portion 46. The step portion 46 andthe convex rim 55 function as a guiding means to prevent up-and-downslippage of the elastic tube C that is arranged along the internalsurface 41.

Next, the structure of the fixing portion 22 of the base 20 will bedescribed with reference to FIG. 7 and FIG. 8. A pair of U-shapedgrooves 22 a are formed on the fixing portion 22 to guide entrance andexit portions of the elastic tube C and a pair of clamp arms 26 a, 26 bto hold the elastic tube C arranged in the U-shaped grooves 22 a areprovided. The clamp arms 26 a, 26 b have crank-shapes that are symmetricto each other. The base ends of the clamp arms 26 a, 26 b are rotatablyattached to a pivot 27 that is vertical to the axis of the drive shaft21 and is parallel to the linear portions 41 b, 41 c of the internalsurface 41. Further, the respective clamp arms 26 a, 26 b have the tipends providing circular cutout portions to hold the elastic tube C andhave small rollers 28 a, 28 b at middle portions. Still further, thebase 20 has a pair of coil springs 29 a, 29 b as a biasing mechanismthat applies bias pressure to the clamp arms 26 a, 26 b so that thesmall rollers 28 a, 28 b move closer and the clamp arms 26 a, 26 brelease the elastic tube C.

When the cover 50 opens, the tip ends of the clamp arms 26 a, 26 brelease the elastic tube C due to the bias pressure applied by the coilsprings 29 a, 29 b as shown in FIG. 8. When the cover 50 closes, theconnecting projection 54 of the cover 50 intrudes between the smallrollers 28 a, 28 b and separates them from each other as shown in FIG.7, which rotates the clamp arms 26 a, 26 b so that the tip ends hold theelastic tube C to fix the elastic tube C to the fixing portion 22against the bias pressure applied by the coil springs 29 a, 29 b.

In addition, a pair of permanent magnets 60 are installed at the loweredge of the rotor body 31 at the positions indicated by the dotted linesin FIG. 1 and FIG. 3. A rotation position sensor 61, which has amagnetic sensor such as a hall element, is mounted on the back surfaceof the casing 40 in the space between the casing 40 and the base 20. Therotation position sensor 61 is located so that it can detect themagnetic flux of the permanent magnets 60.

On the other hand, a permanent magnet 62 is installed on the lower endof the clamp arm 26 a and an arm position sensor 63 having a magneticsensor is mounted on the fixing portion 22 to detect the magnetic fluxof the permanent magnet 62.

The outputs of the sensors 61 and 63 are checked by a controller (notshown). The output of the rotation position sensor 61 is used to detectthe rotation position of the rotor portion 30 during operation of thetube pump 1. The output of the arm position sensor 63 is used todetermine whether the cover 50 opens or closes.

Next, the function of the tube pump 1 that is constructed as above willbe described. During operation of the tube pump 1, an operator arrangesthe elastic tube C along the internal surface 41 of the casing 40,closes the cover 50 and turns on a operation switch (not shown). Whenthe cover 50 is closed, as shown in FIG. 1 and FIG. 2, the casing 40relatively moves leftward in the drawings with respect to the base 20 tothe operating position where the roller 34 b deforms the elastic tube C.Further, the connecting projection 54 of the cover 50 intrudes betweenthe small rollers 28 a, 28 b, which rotate the clamp arms 26 a, 26 b tohold the elastic tube C to the fixing portion 22 at the entrance andexit points as shown in FIG. 7. The controller checks the output fromthe arm position sensor 63. When the controller determines that thecover 50 closes and the clamp arm 26 a holds the elastic tube C, itapplies electric current to the motor 10 to rotate. The rotation of themotor 10 is transferred via the reduction gear 11 to the drive shaft 21,which rotates the rotor portion 30 attached to the drive shaft 21.Assuming that the rotor portion 30 rotates in the counterclockwisedirection in FIG. 1, the roller 34 a contacts the elastic tube C whenthe roller 34 a comes the position opposite to the linear portion 41 cof the internal surface 41. The roller 34 a revolves both on therotating shaft 33 a and around the drive shaft 21 with deforming theelastic tube C by the pressure caused by the compression spring (notshown) arranged between the roller holder 32 a and the rotor body 31.The elastic tube C is squeezed as the roller 34 a advances to thesemicircular portion 41 a and the linear portion 41 b, the liquid in thetube flows in the counterclockwise direction and is pushed out to theexit side. The other roller 34 b contacts the elastic tube C just beforethe roller 34 a comes apart from the elastic tube C. The roller 34 bsends out the liquid in the tube in the same manner as the roller 34 a.With this construction, since the rollers 34 a and 34 b alternatelysqueeze the elastic tube C, the tube pump 1 can continuously send outthe liquid.

When an operator stops the tube pump 1, the operator turns off theoperation switch. The controller detects the output signal from therotation position sensor 61 and continues to apply electric currentuntil a predetermined time elapsed after detecting the output signalfrom the rotation position sensor 61, and then cuts the electriccurrent. The predetermined time is an interval from the detection of theoutput signal of the rotation position sensor 61 to the arrival of therotor portion 30 to the position where the rollers 34 a and 34 b alignin the X-direction as shown in FIG. 1.

As described above, since the rotor portion 30 is controlled so that oneroller stops at the midpoint of the semicircular portion 41 a of thecasing 40, the rollers 34 a and 34 b come apart from the elastic tube bythe movement of the moving mechanism, which allows easy exchange of theelastic tube.

When the elastic tube C is exchanged, the operator stops the rotation ofthe rotor portion 30 and open the cover 50. Opening the cover 50 movesthe casing 40 rightward in FIG. 4 and FIG. 6 with respect to the base20, which locates the roller 34 b apart from the elastic tube C.Further, since the connecting projection 54 of the cover 50 gets out ofthe position between the small rollers 28 a and 28 b as shown in FIG. 8,the clamp arms 26 a and 26 b rotate by the tension of the compressionsprings 29 a and 29 b, which moves the tip ends off the elastic tube C.Under this condition, the elastic tube C can be easily removed andexchanged.

With the above-described structure, since the casing 40 to which largepressure is applied is not separated, the structural strength becomeslarger, which keeps the casing intact even if it is made from plastic.Further, since the casing 40 moves and the clamp arms 26 a, 26 b rotatein response to the opening/closing operations of the cover 50, theelastic tube C can be easily exchanged.

1. A tube pump comprising: a base that holds a drive shaft that connectswith and is driven by a motor; a rotor portion that rotates with saiddriving shaft, said rotor portion having a pair of rollers each of whichhas a rotating shaft decentered from said drive shaft; a casing having aU-shaped internal surface that includes a semicircular portion andparallel linear portions connected to both ends of said semicircularportion along which an elastic tube is arranged, said casing beingmounted on said base so that said casing can slide with respect to saidbase in a direction parallel to said linear portions; a cover that isrotatably mounted on said casing at the outside of said semicircularportion, said cover covering the portion surrounded by said internalsurface at its closing position; a moving mechanism including a rackthat is formed on said base and a pinion that is fixed to a rotationshaft of said cover and engages with said rack, said moving mechanismmoving said casing with respect to said base to an operating positionwhere said roller deforms said elastic tube arranged along said internalsurface when said cover closes, and said moving mechanism moving saidcasing with respect to said base to an exchange position where saidroller comes apart from said elastic tube when said cover opens.
 2. Thetube pump according to claim 1, wherein said internal surface of saidcasing has a step portion so that the diameter of the semicircularportion at the side of the cover becomes larger than the other side, andsaid cover has a convex rim, which can insert inside said internalsurface, is formed on said cover at the position opposite to said stepportion, whereby said step portion and said convex rim function as ameans for guiding said elastic tube that is arranged along said internalsurface.
 3. The tube pump according to claim 1 or 2, further comprising:a pair of clamp arms that is mounted on said base to hold entrance andexit portions of said elastic tube to the pump, respectively, the baseend of each of said clamp arm being rotatably attached to a pivot thatis vertical to the axis of said drive shaft and is parallel to saidlinear portions, each of said clamp arm having a tip end that is formedto hold said elastic tube and having a small roller at a middle portionthereof; a biasing mechanism that applies bias pressure to said clamparms so that said small rollers move closer and said clamp arms releasesaid elastic tube; and a connecting projection that is formed on saidcover to intrude between said small rollers when said cover closes,wherein said connecting projection of the cover intrudes between saidsmall rollers and separates them from each other, which rotates theclamp arms against the bias pressure applied by the biasing mechanismwhen the cover closes.
 4. The tube pump according to one of claims 1through 3, further comprising: a permanent magnet mounted on said rotorportion at the position opposite to the casing; and a magnetic sensorinstalled on either of said casing and said base for detecting magneticflux of said permanent magnet to determine the rotation position of saidrotor portion.